Coloured axial computed tomography (CT) scan of the pelvis and hips of a 42-year-old overweight female patient. The patient had pain in the groin on the right and left side. The scan shows the presence of hypodensities of the femoral heads suggestive of osteonecrosis of the femoral heads (avascular osteonecrosis). Osteonecrosis is a condition is caused by poor blood supply to the affected area and the bone marrow. It most commonly affects the bones of the hips, knees and face. It can cause the bone and joint to collapse, and hip joints may need replacing or resurfacing.